Optimizing raw material composition and alkali content in low silicon-aluminum tailings-based geopolymers

Abstract

This study delves into the effective utilization of low silicon–aluminum tailings, exploring their potential for large-scale applications in one-part (‘just add water’) geopolymers. Optimizing the raw material composition and alkali content is crucial. Higher slag content enhanced gel production and polymerization, resulting in a more homogeneous structure dominated by C-(A)-S-H gels with stronger bonding. While increased metakaolin content forms more zeolite phases and exhibited an incompatible structure filled with N-A-S-H gels with weaker bonding. Alkali concentrations also play a significant role in promoting tailings dissolution and gel polymerization. Excessive levels, however, hinder the process and restrict strength development. Ultimately, a reasonable mechanical strength of 52.8 MPa was achieved. The geopolymer paste effectively immobilizes Pb and Zn, demonstrating impressive immobilization rates of 97% and 91%, respectively. The chemical speciation analysis reveals the conversion from unstable to stable state. These findings highlight the potential applicability of low silicon–aluminum tailings in geopolymers.